ᐅ Constructing a Cost-Effective Retaining Wall / Slope Stabilization
Created on: 27 Feb 2019 13:50
A
abc12345
Hello everyone,
The weather is steadily improving, so it’s time to start planning the outdoor area. Parts of the property will need to be filled in. The site has already been surveyed, and leveling at the lowest point would require approximately 2 meters (6.5 feet) of fill soil.
There are gardens adjacent to the property on all sides, so I will need to build a retaining wall accordingly.
I have already spoken with the local building materials supplier. He suggested simply making a foundation by excavating 1 meter (3.3 feet) deep, then adding a 20 cm (8 inches) layer of crushed stone, followed by 80 cm (31.5 inches) of reinforced concrete. On top, concrete blocks would be placed, reinforced with rebar and filled with concrete. He recommended using blocks sized 26 cm or 29 cm (10 or 11.5 inches), but said he could not provide structural calculations or any official advice. He quoted me a material cost of about 3,500 euros.
Nothing was mentioned about installing drainage. I’m also unsure where the water would be directed since all sides border neighboring properties. Or did I misunderstand the purpose of drainage—is it to carry water away from the retaining wall to somewhere else?
Now my question is whether there might be other, possibly more cost-effective ways to do this? Precast L-shaped concrete elements are available here, but they cost about three times as much and require a mini-excavator for installation.
Another option I considered is to reduce the wall height to 1 meter (3.3 feet) and create a steep slope up to the fill level. However, I’m not sure how steep the slope can be without causing sliding. The property will later be enclosed with a dense hedge for privacy. As far as I understand, the wall must be set back 2 meters (6.5 feet) from the property boundary to avoid problems with height restrictions, especially because the ground has already been raised by 2 meters (6.5 feet).
I want to minimize the amount of space lost to make the most of the property, but I also want to keep costs relatively low since there are many other projects planned.
Since I can’t see the wall from my side and the neighbor is a daycare center, appearance is not a major concern for me.
Maybe you have some ideas or tips on the best way to approach this.
Thank you in advance for your help.
The weather is steadily improving, so it’s time to start planning the outdoor area. Parts of the property will need to be filled in. The site has already been surveyed, and leveling at the lowest point would require approximately 2 meters (6.5 feet) of fill soil.
There are gardens adjacent to the property on all sides, so I will need to build a retaining wall accordingly.
I have already spoken with the local building materials supplier. He suggested simply making a foundation by excavating 1 meter (3.3 feet) deep, then adding a 20 cm (8 inches) layer of crushed stone, followed by 80 cm (31.5 inches) of reinforced concrete. On top, concrete blocks would be placed, reinforced with rebar and filled with concrete. He recommended using blocks sized 26 cm or 29 cm (10 or 11.5 inches), but said he could not provide structural calculations or any official advice. He quoted me a material cost of about 3,500 euros.
Nothing was mentioned about installing drainage. I’m also unsure where the water would be directed since all sides border neighboring properties. Or did I misunderstand the purpose of drainage—is it to carry water away from the retaining wall to somewhere else?
Now my question is whether there might be other, possibly more cost-effective ways to do this? Precast L-shaped concrete elements are available here, but they cost about three times as much and require a mini-excavator for installation.
Another option I considered is to reduce the wall height to 1 meter (3.3 feet) and create a steep slope up to the fill level. However, I’m not sure how steep the slope can be without causing sliding. The property will later be enclosed with a dense hedge for privacy. As far as I understand, the wall must be set back 2 meters (6.5 feet) from the property boundary to avoid problems with height restrictions, especially because the ground has already been raised by 2 meters (6.5 feet).
I want to minimize the amount of space lost to make the most of the property, but I also want to keep costs relatively low since there are many other projects planned.
Since I can’t see the wall from my side and the neighbor is a daycare center, appearance is not a major concern for me.
Maybe you have some ideas or tips on the best way to approach this.
Thank you in advance for your help.
Winniefred28 Feb 2019 17:58And I have to say, we are usually more of the do-it-yourself type. But this is simply too big of a task and better suited for professionals. I did a lot of research and, at least in our case, came to the conclusion that we need experts (structural engineering, backfilling, drainage, foundation, etc.). The goal is for it to last as long as possible, so you never have to worry about it again, but rather that other people will only need to think about it in 100 years or more.
Winniefred schrieb:
We are facing a similar problem. Our wall is about 50m (164 feet) long, and roughly the last 15-20m (49-66 feet) need repairs. Since the property slopes slightly, the wall is 1.2m (4 feet) high at the highest point and gradually gets lower towards the front. Behind it, there are old privet hedges and shrubs everywhere (the land belongs to the city, and next to it is a sidewalk).
So far, I haven’t found a practical and cost-effective solution. I’ve come to accept that one day we will have to invest a significant amount and hire a large company to handle it. The wall is 100 years old, and over approximately 8m (26 feet) it is already leaning slightly inward, with plaster falling off everywhere, so it cannot last much longer. Since our backyard is quite narrow, I have moved away from the idea of creating a slope. That would cause us to lose too much usable space. Plus, the existing structure would also need support first. You can’t just tear down the old wall carelessly… at least not without facing a number of challenges.
We also have the problem that vehicles, especially large ones, cannot access the site. Considering how many tons of materials are required, doing it ourselves seems almost impossible. It really requires manpower and machinery.
To make things more complicated, there is a streetlight nearby, so we first have to request the location plans for the power lines from the civil engineering department.
To be honest, projects like this are really no fun—neither financially nor in terms of effort.The streetlight can be removed. Our municipality arranged this. The costs for removal, transport, storage, and reinstallation were, if I remember correctly, around 3,000 euros.
The slope must be stabilized before the wall can be replaced. It might be cheaper to install a new wall in front of the existing one. I wouldn’t attempt this myself.
H
HilfeHilfe1 Mar 2019 07:07The structural engineering aspect is overrated. Our house was built on compacted soil, then we had a slope and built a retaining wall (highest point 2 meters (6.5 feet)) and filled it with soil afterward.
What pressure could there be when the house was already standing on the ground?
Also, this idea that you have to dig 1 meter (3.3 feet) deep and make it frost-proof, etc.
My father was a bricklayer; he laughed about that. He said, dig a trench 30 cm (12 inches) deep, put 20 cm (8 inches) of gravel which you compact, then the first concrete layer, and after that set the first stone (10 cm (4 inches) below ground / 10 cm (4 inches) above ground).
Then you do it like Lego, always staggered.
As I said, it was fun. You just need someone who knows how to use a plumb line so the wall won’t be crooked in the long run...
That was the only challenge.
What pressure could there be when the house was already standing on the ground?
Also, this idea that you have to dig 1 meter (3.3 feet) deep and make it frost-proof, etc.
My father was a bricklayer; he laughed about that. He said, dig a trench 30 cm (12 inches) deep, put 20 cm (8 inches) of gravel which you compact, then the first concrete layer, and after that set the first stone (10 cm (4 inches) below ground / 10 cm (4 inches) above ground).
Then you do it like Lego, always staggered.
As I said, it was fun. You just need someone who knows how to use a plumb line so the wall won’t be crooked in the long run...
That was the only challenge.
HilfeHilfe schrieb:
Statics are overrated. [...]
What is supposed to be pushing there?? Especially if the house has already been standing on the ground?? In discussions about retaining walls, I often feel like I’m among people who have never seen a landslide after heavy rain and who only studied a bit of optics and electronics in physics class.
On one side, there is (supposedly) solid mass (plus potential energy), and on the other side, just air: of course that exerts pressure — even if the internal cohesion of the mass “resists” it (but then it’s not yet critical). If it becomes too wet (or experiences similar impacts), then being completely rigid and tipping over is still the bravest thing the wall can do.
The goalkeeper still holds up, the hair gel stays in place through all weather, but unfortunately, based on my father’s experience, the wall does not.
Three things help here, best used together as a trio: anchoring (which is exactly what L-shaped retaining blocks do), an inclination against the pressure direction, and reinforcement (of the mass itself!) with root systems or similar.
Reinforcement inside the wall doesn’t make it stronger, only stiffer. That is good and useful as a fourth measure but does not replace the first three. The stiffness of the wall only determines the difference between crumbling and tipping. Since crumbling requires less force and makes the forces visible, stiffness is mistakenly believed by laypersons to be sufficient except in extreme events.
Forces typically become apparent only when one side exceeds the other significantly—but denying their existence up until then can still be a serious mistake.
I dare say you can quite reliably tell whether retaining wall builders are physics teachers, business economists, or computer scientists.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
Winniefred1 Mar 2019 18:00Very well explained. On our wall, you can see what happens when it is just done carelessly. Water and frost cause the wall to deteriorate, the wall starts to lean, the plaster falls off (even the plaster that was renewed falls off again in large sheets), and even individual bricks simply break. Of course, everyone has to decide for themselves, but in this case, I definitely recommend doing it properly from the start.
Winniefred schrieb:
On our wall, you can see what happens when it’s just thrown together carelessly. Water and freeze-thaw cycles cause decay through the wall, But you’re probably referring to a wall made of mortared bricks or blocks – that’s a whole different category. I was rather referring to walls made of formwork blocks, where this kind of deterioration comparable to pothole formation does not occur, and the phenomena you described don’t happen in the same way.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
Similar topics